You can change them to 6700K bulbs if you want; it will not increase the amount of light you have. It will change the look of your aquarium, as 6700K is significantly whiter (with a tint of blue).

What "would" change the amount of light in my tank? I have seen no growth, the tank looks dark, and not sure if light is my problem, or my hard water. (unable to test gh/kh atm-gotta buy a kit on the 1st)

I am feeling a little distressed, it has been since 12/20, and the only new growth I have are, 1 leaf on an Anubas, New roots on my Swords near the top leaves, and frogbit having babies (which are starting to be my favorite since they are the only plants seeming to thrive. .
My Vals melted, my egra densa melted, my Bacopa Carolina looks the same since it was planted, and just about ready to give up.